The present invention relates to a membrane switch used to perform an input operation in electronics devices, such as remote controllers, keyboards, cellular telephones, personal digital assistants (PDAs), and digital still cameras (DSCs), a method for manufacturing a membrane switch, and a contact switch including a membrane switch.
Membrane switches, which are used to perform an input operation in electronics devices, are known in the prior art. Japanese Laid-Open Patent Publication No. 2003-45262 describes a membrane switch. This membrane switch includes first and second substrates, which are arranged to face each other. Two electrodes are arranged on the first and second substrates in a manner that the electrodes face each other. An electric circuit including a resistive element is formed on the first substrate. The resistive element is made from a conductive material. A resist film is further applied to the first substrate to protect the electric circuit from moisture. The resist film has an opening that exposes the electrodes and end portions of wires in the electric circuit from the surface of the first substrate. The wire end portions are connected to a power supply circuit through the opening.
The resistive element is formed by applying the conductive material and drying the applied conductive material. Further, the resistive element is covered by the resist film. The degree of dryness of the conductive material forming the resistive element differs depending on the degree to which a resist material is dried to form the resist film. Thus, the resistance of the resistive element easily changes depending on the degree of dryness of the resist material. As a result, when using membrane switches in the prior art, the resistance of resistance elements differs greatly between products and between resistors in the same product.